Laminated substrate having piezoelectric film, element having piezoelectric film and method for manufacturing this laminated substrate

ABSTRACT

There is provided a laminated substrate having a piezoelectric film, including: a substrate; and a piezoelectric film provided on the substrate interposing a base film, wherein the piezoelectric film has an alkali niobium oxide based perovskite structure represented by a composition formula of (K 1-x Na x )NbO 3  (0&lt;x&lt;1) and preferentially oriented in (001) plane direction, and a sound speed of the piezoelectric film is 5100 m/s or more.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Divisional of U.S. Pat. Application No.16/628,524, filed on Jan. 3, 2020, which claims priority under 37 U.S.C.§ 371 to International Patent Application No. PCT/JP2018/023864, filedJun. 22, 2018, which claims priority to and the benefit of JapanesePatent Application No. 2017-136447, filed on Jul. 12, 2017. The contentsof these applications are hereby incorporated by reference in theirentireties.

TECHNICAL FIELD

The present disclosure relates to a laminated substrate having apiezoelectric film, an element having a piezoelectric film, and a methodfor manufacturing this laminated substrate.

DESCRIPTION OF RELATED ART

A piezoelectric material is utilized widely for a functional electroniccomponent such as a filter device. For example, potassium sodium niobate(KNN) is used as the piezoelectric material (see patent documents 1 and2, for example). Recently, it is strongly required to provide thepiezoelectric material suitable for application to the filter device ofa high frequency band.

PRIOR ART DOCUMENT Patent Document

-   Patent document 1: Japanese Patent Laid Open Publication    No.2007-184513-   Patent document 2: Japanese Patent Laid Open Publication    No.2008-159807

SUMMARY Problem to be Solved by Disclosure

An object of the present disclosure is to provide a piezoelectric filmsuitable for application to a filter device of a high frequency band,and a related technique thereof.

Means for Solving the Problem

According to an aspect of the present disclosure, there is provided alaminated substrate having a piezoelectric film and a related techniquethereof, including:

-   a substrate; and-   a piezoelectric film provided on the substrate interposing a base    film,-   wherein the piezoelectric film has an alkali niobium oxide based    perovskite structure represented by a composition formula of    (K_(1-x)Na_(x))NbO₃ (0<x<1) and preferentially oriented in (001)    plane direction, and-   a sound speed of the piezoelectric film is 5100 m/s or more.

Advantage of the Disclosure

According to the present disclosure, there is provided a piezoelectricfilm suitable for application to a filter device of a high frequencyband, and a related technique thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing an example of a cross-sectional structure of alaminated substrate according to an embodiment of the presentdisclosure.

FIG. 2 is a view showing a modified example of the cross-sectionalstructure of the laminated substrate according to an embodiment of thepresent disclosure.

FIG. 3 is a schematic constitution view of a piezoelectric film deviceaccording to an embodiment of the present disclosure.

FIG. 4 is a view showing a modified example of the cross-sectionalstructure of the piezoelectric film device according to an embodiment ofthe present disclosure.

FIG. 5 is a view showing a measurement principle of a sound speed of apiezoelectric film according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE An Embodiment of the PresentDisclosure

An embodiment of the present disclosure will be described hereafter,with reference to drawings.

A Constitution of a Laminated Substrate

As shown in FIG. 1 , a laminated substrate 10 according to the presentembodiment is constituted as a laminate including a substrate 1, a basefilm 7 provided on the substrate 1, a piezoelectric film (piezoelectricthin film) 3 provided on the base film 7, and a top electrode film 4provided on the piezoelectric film 3.

As the substrate 1, a single-crystal silicon (Si) substrate 1 a on whicha surface oxide film (SiO₂-film) 1 b such as a thermal oxide film or aCVD (Chemical Vapor Deposition) oxide film is provided (formed), namely,a Si-substrate having the surface oxide film, can be used preferably.Further, as shown in FIG. 2 , a Si-substrate 1 a having an insulatingfilm 1 d provided on its surface may also be used as the substrate 1,the insulating film 1 d containing an insulating material other thanSiO₂. Further, a Si-substrate 1 a in which Si-(100) plane or Si-(111)plane, etc., is exposed on a surface thereof, namely, a Si-substrate nothaving the surface oxide film 1 b or the insulating film 1 d may also beused as the substrate 1. Further, an SOI (Silicon On Insulator)substrate, a quartz glass (SiO₂) substrate, a gallium arsenide (GaAs)substrate, a sapphire (Al₂O₃) substrate, a metal substrate containing ametal material such as stainless steel may also be used as the substrate1. The single-crystal Si-substrate 1 a has a thickness of 300 to 1000 µmfor example, and the surface oxide film 1 b has a thickness of 5 to 3000nm for example.

The base film 7 can be formed (provided, deposited) using platinum (Pt)for example. The base film 7 is a single-crystal film or a poly-crystalfilm (they are also referred to as Pt-film hereafter). Preferably,crystals constituting the Pt-film are preferentially oriented in (111)plane direction with respect to a surface of the substrate 1. Namely, itis preferable that a surface of the Pt-film (a surface which is a baseof the piezoelectric film 3) is mainly constituted of Pt-(111) plane.The Pt-film can be formed using a method such as a sputtering method, oran evaporation method. In addition to Pt, the base film 7 may also beformed using various metals such as gold (Au), ruthenium (Ru), oriridium (Ir), an alloy mainly composed of the above various metals, or ametallic oxide such as strontium ruthenate (SrRuO₃) or lanthanum nickeloxide (LaNiO₃), etc. An adhesion layer 6 mainly composed of titanium(Ti), tantalum (Ta), titanium oxide (TiO₂), or nickel (Ni), etc., forexample is formed between the substrate 1 and the base film 7 in orderto enhance an adhesion between them. The adhesion layer 6 can be formedusing a method such as a sputtering method, or an evaporation method.The base film 7 has a thickness of 100 to 400 nm for example, and theadhesion layer 6 has a thickness of 1 to 200 nm for example.

The piezoelectric film 3 can be formed (provided, deposited) usingalkali niobium oxide which contains for example, potassium (K), sodium(Na), and niobium (Nb), and which is represented by a compositionformula of (K_(1-x)Na_(x))NbO₃. Namely, the piezoelectric film 3 can beformed using potassium sodium niobate (KNN). A coefficient x [=Na/(K+Na)] in the above composition formula is a value in a range of0<x<1, preferably 0.4≤x≤0.7. The piezoelectric film 3 is a poly-crystalfilm of KNN (also referred to as KNN-film 3 hereafter). A crystalstructure of KNN is a perovskite structure.

Preferably, crystals constituting the KNN-film 3 are preferentiallyoriented in (001) plane direction with respect to the surface of thesubstrate 1. Namely, it is preferable that a surface of the KNN-film 3(a surface which is a base of the top electrode film 4) is mainlyconstituted of KNN-(001) plane. By forming the KNN-film 3 directly onthe Pt-film (base film 7) preferentially oriented in (111) planedirection with respect to the surface of the substrate 1, crystalsconstituting the KNN-film 3 can be easily preferentially oriented in(001) plane direction with respect to the surface of the substrate 1.For example, 85 % or more of crystals of a crystal group constitutingthe KNN-film 3 can be oriented in (001) plane direction with respect tothe surface of the substrate 1, and thereby a region of 85% or more ofthe surface of the KNN-film 3 can be KNN-(001) plane. Namely, a(001)-orientation ratio of the KNN-film 3 can be 85 % or more.

The KNN-film 3 can be formed using a method such as a sputtering method,a PLD (Pulsed Laser Deposition) method, or a sol-gel method. Acomposition ratio of the KNN-film 3 can be adjusted by controlling acomposition of a target material used during sputtering, for example.The target material can be produced by mixing and firing K₂CO₃-powder,Na₂CO₃-powder, Nb₂O₅-powder, etc., for example. In this case, thecomposition of the target material can be controlled by adjusting amixed ratio of K₂CO₃-powder, Na₂CO₃-powder, Nb₂O₅-powder, etc.

In the KNN-film 3, its sound speed is 5100 m/s or more, preferably 5700m/s or more, and more preferably 5800 m/s or more.

In this specification, the sound speed is measured using BrillouinOscillation method. FIG. 5 shows an example of a measurement principleview of the sound speed by Brillouin Oscillation method. As exemplifiedin FIG. 5 , first, the surface of the KNN-film 3 is irradiated with apump light and a probe light which are femtosecond laser pulsed lightfor example. The pump light is the light for exciting a sound wave inthe KNN-film 3. Specifically, the surface of the KNN-film 3 isirradiated with the pump light vertically to the surface of the KNN-film3, to thereby increase locally and instantaneously a temperature in thevicinity of the surface of the KNN-film 3 at an irradiation position ofthe pump light. The sound wave (ultrasonic pulse) is excited in theKNN-film 3, due to a thermal stress generated at the above position.This sound wave is a longitudinal wave which mainly propagates in avertical direction to the surface of the KNN-film 3. A part of the soundwave which propagates in the KNN-film 3 toward the base film 7, isreflected at an interface between the KNN-film 3 and the base film 7,and returns to the surface (vicinity of the surface) of the KNN-film 3.As a result, the surface of the KNN-film 3 is deformed. The probe lightis the light for irradiating the irradiation position of the pump lighton the surface of the KNN-film 3 at a prescribed angle with respect tothe surface of the KNN-film 3. A prescribed delay time may be given tothe probe light. The reflected light of the probe light is continuouslydetected by a detector, and its reflectance is continuously measured, tothereby obtain a function of a delay time between the pump light and theprobe light, and the reflectance of the probe light. When the surface ofthe KNN-film 3 is deformed by the reflected light of the pump light asdescribed above, the reflectance of the reflected light of the probelight is varied, and a peak (echo) occurs. As a result, the time fromthe irradiation of the pump light to the occurrence of the peak,coincides with a propagation time of the sound wave which propagates inthe KNN-film 3 and returns to the surface of the KNN-film 3. In thisembodiment, since a thickness of the KNN-film 3 is already known, thesound speed of the KNN-film 3 can be calculated based on the timebetween the peaks.

The sound speed of the KNN-film 3 depends on an orientation state in(001) plane direction of the crystals constituting the KNN-film 3 (alsoreferred to as (001)-orientation state of the KNN-film 3 hereafter). Thesound speed of the KNN-film 3 increases as the number of crystalsoriented in (001) plane direction in the KNN-film 3 increase, namely asthe (001)-orientation ratio of the KNN-film 3 becomes higher. Further,the sound speed of the KNN-film 3 decreases as the number of thecrystals oriented in (001) plane direction in the KNN-film 3 decrease,namely as the (001)-orientation ratio of the KNN-film 3 becomes lower.Hereafter, high (001)-orientation ratio of the KNN-film 3 is also called“(001)-high orientation”, and low (001)-orientation ratio of theKNN-film 3 is also called “(001)-low orientation”.

For example, a mixed gas (Ar/O₂-mixed gas) of argon (Ar) gas and oxygen(O₂) gas is used as an atmosphere gas during sputtering of the KNN-film3. However, water existing in a chamber is sometimes mixed in theatmosphere gas although its content is very small. The (001)-orientationstate of the KNN-film 3 greatly depends on a partial pressure of H₂Ocontained in the atmosphere gas during sputtering. The (001)-orientationstate tends to be (001)-high orientation when H₂O-partial pressure islow, and tends to be (001)-low orientation when H₂O-partial pressure ishigh. The (001)-orientation ratio of the KNN-film 3 can be adjusted bycontrolling the partial pressure of H₂O containing in the Ar/O₂-mixedgas during sputtering. The (001)-orientation ratio of the KNN-film 3 canbe 85 % or more by adjusting the H₂O-partial pressure to 1/100 or less,preferably 1/300 or less of a pressure in a growth atmosphere, forexample.

When a later-described piezoelectric film device 30 produced byprocessing the laminated substrate 10, functions as a filter device of ahigh frequency band, the sound speed of the KNN-film 3 is preferablyfast. However, according to a current state of the art, the sound speedof the KNN-film 3 is 6000 m/s or less for example, due to an upper limitof the (001)-orientation ratio of the KNN-film 3, or a mixture ofinevitable impurities into the KNN-film 3 during formation of theKNN-film 3, etc.

An absolute value |d₃₁| of a piezoelectric constant of the KNN-film 3 is90 pm/V or more for example (|d₃₁|≥90 pm/V), preferably 100 pm/V or more(|d₃₁|≥100 pm/V). A thickness of the KNN-film 3 is 0.5 to 5 µm or lessfor example.

The KNN-film 3 may contain an element such as copper (Cu), manganese(Mn), lithium (Li), Ta, antimony (Sb) other than K, Na, Nb in a range of5 at% or less.

The top electrode film 4 can be formed (provided, deposited) usingvarious metals such as Pt, Au, aluminum (Al), or Cu, or an alloy ofthese various metals, for example. The top electrode film 4 can beformed using a method such as a sputtering method, an evaporationmethod, a plating method, or a metal paste method. The top electrodefilm 4 does not greatly affect the crystal structure of the KNN-film 3unlike the base film 7. Therefore, a material and a crystal structure ofthe top electrode film 4, and a method for forming the top electrodefilm 4 are not particularly limited. An adhesion layer mainly composedof Ti, Ta, TiO₂, Ni, etc., for example may be formed between theKNN-film 3 and the top electrode film 4 in order to enhance an adhesionbetween them. The top electrode film 4 has a thickness of 100 to 5000 nmfor example, and the adhesion layer has a thickness of 1 to 200 nm in acase of forming the adhesion layer.

A Constitution of a Piezoelectric Film Device

FIG. 3 shows a schematic constitution view of a device 30 having thepiezoelectric film of the present embodiment (also referred to aspiezoelectric film device 30 hereafter). The piezoelectric film device30 is constituted including at least an element 20 having thepiezoelectric film (also referred to as piezoelectric film element 20hereafter) obtained by forming the above laminated substrate 10 into aprescribed shape, and a voltage application means 11 a and a voltagedetection means 11 b which are connected to the piezoelectric filmelement 20.

The piezoelectric film element 20 has pattern electrodes obtained byforming the top electrode film 4 into a prescribed pattern. Thepiezoelectric film element 20 has a pair of positive-negative patternelectrodes 4 p ₁ which are input-side electrodes, and a pair ofpositive-negative pattern electrodes 4 p ₂ which are output-sideelectrodes. A comb-shaped electrode (IDT: Inter Digital Transducer) isused as the pattern electrodes 4 p ₁ and 4 p ₂, for example.

By connecting the voltage application means 11 a between the patternelectrodes 4 p ₁ and connecting the voltage detection means 11 b betweenthe pattern electrodes 4 p ₂, the piezoelectric film device 30 canfunction as a filter device such as a SAW filter. By applying a voltagebetween the pattern electrodes 4 p ₁ using the voltage application means11 a, SAW can excite on the surface of the KNN-film 3. A frequency ofexcited SAW can be adjusted by adjusting a pitch between the patternelectrodes 4 p ₁, for example. For example, the frequency of SAW becomeshigh as a pitch of IDT as the pattern electrodes 4 p ₁ is short, and thefrequency of SAW becomes low as the above pitch is long. A voltage isgenerated between the pattern electrodes 4 p ₂, due to SAW having aprescribed frequency (frequency component) determined according to thepitch of IDT as the pattern electrodes 4 p ₂ in the SAW which is excitedby the voltage application means 11 a, propagates in the KNN-film 3, andreaches the pattern electrodes 4 p ₂. By detecting this voltage usingthe voltage detection means 11 b, SAW having a prescribed frequency inthe excited SAW can be extracted. The “prescribed frequency” as usedhere can include not only a prescribed frequency but also a prescribedfrequency band in which a center frequency is prescribed frequency.

A Method for Manufacturing a Laminated Substrate, a Piezoelectric FilmElement, and a Piezoelectric Film Device

Next, a method for manufacturing the above laminated substrate 10 willbe described. First, the base film 7 is formed on any one of mainsurfaces of the substrate 1. It is also acceptable to prepare thesubstrate 1 on which the base film 7 is formed in advance on any one ofits main surfaces. Next, the KNN-film 3 is formed on the base film 7using the sputtering method for example. Thereafter, the top electrodefilm 4 is formed on the KNN-film 3 using the sputtering method forexample, and therefore the laminated substrate 10 is obtained. Then, thelaminated substrate 10 is formed into a prescribed shape, for example,the top electrode film 4 is formed into the pattern electrodes 4 p ₁ and4 p ₂ by etching, etc., and therefore the piezoelectric film element 20is obtained. Further, the voltage application means 11 a is connectedbetween the pattern electrodes 4 p ₁ of the piezoelectric film element20, and the voltage detection means 11 b is connected between thepattern electrodes 4 p ₂ of the piezoelectric film element 20, andtherefore the piezoelectric film device 30 is obtained.

Effect Obtained by the Present Embodiment

According to the present embodiment, one or more of the followingeffects can be obtained.

(a) Since the sound speed of the KNN-film 3 is 5100 m/s or more, aresonance frequency of the piezoelectric film device 30 produced byprocessing the laminated substrate 10 having the KNN-film 3 can be highfrequency. Thereby, the piezoelectric film device 30 can be suitablyapplied to a filter device of a high frequency band compared to apiezoelectric film device obtained by processing a laminated substratehaving conventional KNN-film. Namely, since the sound speed of theKNN-film 3 is fast, the piezoelectric film device 30 can suitablyfunction as a high frequency filter.

When the sound speed of the KNN-film 3 is less than 5100 m/s, it isdifficult to use the piezoelectric film device as the high frequencyfilter, in some cases. Further, even in a case that such a piezoelectricfilm device can be used as the high frequency filter, a filter propertyof this high frequency filter becomes low, in some cases.

(b) Since the sound speed of the KNN-film 3 is 5100 m/s or more, thepiezoelectric film device 30 can be actuated at a higher frequencywithout shortening the pitch of the pattern electrodes 4p, when thethickness of the KNN-film 3 is constant. Namely, when the piezoelectricfilm device 30 capable of actuating at high frequency is produced, it isnot necessary to make a minute pattern electrodes 4p.

(c) Since the (001)-orientation ratio of the KNN-film 3 is 85% or more,the sound speed of the KNN-film 3 can be 5700 m/s or more. Further, the(001)-orientation ratio of the KNN-film 3 is 90 % or more, the soundspeed of the KNN-film 3 can be 5800 m/s or more. It is already found bythe present inventors that the sound speed of the KNN-film 3 is 5650 m/swhen the (001)-orientation ratio of the KNN-film 3 is 78 %, and thesound speed of the KNN-film 3 is 5820 m/s for example when the(001)-orientation ratio of the KNN-film 3 is 92 %.

(d) Since the absolute value |d₃₁| of the piezoelectric constant of theKNN-film 3 is 90pm/V or more, the high frequency filter can be a lowloss filter, or a reduction of a detecting sensitivity of frequency canbe prevented, when the piezoelectric film device 30 is used as the highfrequency filter. Namely, since the KNN-film 3 has excellentpiezoelectric property, a performance of the piezoelectric film device30 can be enhanced.

Here, for reference, conventional laminated substrate using for the highfrequency filter will be described.

Conventionally, for example, a piezoelectric film device using alaminated substrate having a piezoelectric film made of aluminum nitride(AlN) (also referred to as AlN-film hereafter), functions as the highfrequency filter. However, there is a problem as follows: although asound speed of the AlN-film is faster than that of the KNN-film, anabsolute value |d₃₁| of a piezoelectric constant of the AlN-film issmaller than that of the KNN-film. For example, although the sound speedof the AlN-film is 10000 m/s or more, the absolute value |d₃₁| of thepiezoelectric constant of the AlN-film is about 5 pm/V. Therefore, whenthis piezoelectric film device functions as the high frequency filter,this filter becomes low performance filter.

Further, for example, it is also conceivable that a piezoelectric filmdevice using a laminated substrate having a piezoelectric film made oflead zirconate titanate (PZT) (also referred to as PZT-film hereafter),functions as the high frequency filter. However, there is a problem asfollows: although the PZT-film has the piezoelectric property similar tothat of the KNN-film, a sound speed of the PZT-film is slower than thatof the KNN-film. For example, although an absolute value |d₃₁| of apiezoelectric constant of the PZT-film is 90 pm/V or more, the soundspeed of the PZT-film is about 4000 to 5000 m/s. Therefore, it isnecessary to make a minute pitch between the pattern electrodes comparedto the pitch of the piezoelectric film device having the above KNN-film,in order to function the piezoelectric film device having the PZT-filmas the high frequency filter. There is also a problem as follows: sincethe pitch of the pattern electrodes in the high frequency filter ismicrometer (µm) order, in the piezoelectric film device having thePZT-film, it is very difficult to make a minute pitch between thepattern electrodes with high accuracy.

Modified Example

The present embodiment is not limited to the abovementioned embodiment,and can be modified as the following modified examples.

The above piezoelectric film device 30 may be applied to a filter deviceutilizing a bulk acoustic wave. For example, the piezoelectric filmdevice 30 may function as a Bulk Acoustic Wave (BAW) filter such as apiezoelectric thin film acoustic resonator (FBAR: Film Bulk AcousticResonator). FIG. 4 shows a schematic constitution view of apiezoelectric film device 30A capable of functioning as a FBAR filter.As shown in FIG. 4 , the piezoelectric film device 30A is constitutedincluding at least a piezoelectric film element 20A obtained by forminga laminated substrate 10A into a prescribed shape, and the voltageapplication means 11 a and the voltage detection means 11 b which areconnected to the piezoelectric film element 20A.

The laminated substrate 10A is constituted as a laminate including thesubstrate 1, the bottom electrode film 2 provided on the substrate 1,the KNN-film (piezoelectric film) 3 provided on the bottom electrodefilm 2, and the top electrode film 4 provided on the KNN-film 3. Thebottom electrode film 2 can be the same constitution as the above basefilm 7. The KNN-film 3 has a region where the thickness is thin (alsoreferred to as thin area hereafter). Further, the laminated substrate10A has a cavity 8 for oscillating freely the KNN-film 3. In thismodified example, the cavity 8 is formed by forming a through hole onthe substrate 1. The cavity 8 may be formed after forming the KNN-film 3and before forming the top electrode film 4, or may be formed afterforming the top electrode film 4. The cavity 8 is not limited to theconstitution exemplified in FIG. 4 , and may be publicly-known variousconstitutions. Further, in the piezoelectric film element 20A, the topelectrode film 4 is not required to be IDT, and the top electrode film 4may be formed into a prescribed shape (pattern).

In the piezoelectric film device 30A, the voltage application means 11 aand the voltage detection means 11 b are connected between the bottomelectrode film 2 and the top electrode film 4, respectively. In thismodified example, the voltage application means 11 a is connected to thetop electrode film 4 located on an area other than the thin area of theKNN-film 3, and the voltage detection means 11 b is connected to the topelectrode film 4 located on the thin area of the KNN-film 3.

By applying a voltage between the bottom electrode film 2 and the topelectrode film 4 using the voltage application means 11 a, BAW isexcited in the KNN-film 3. A frequency of BAW, namely, a resonancefrequency of the KNN-film 3 can be adjusted by adjusting a thickness ofthe region other than the thin area of the KNN-film 3, for example. Theresonance frequency of the KNN-film 3 (BAW) becomes high as thethickness of the KNN-film 3 becomes thin, and the resonance frequency ofthe KNN-film 3 becomes low as the thickness of the KNN-film 3 becomesthick. A voltage is generated between the bottom electrode film 2 andthe top electrode film 4, due to BAW having a prescribed frequency(frequency component) determined according to the thickness of the thinregion of the KNN-film 3, etc., in the BAW which is excited by thevoltage application means 11 a, propagates in the KNN-film 3, andreaches an out-put side electrode. By detecting this voltage using thevoltage detection means 11 b, BAW having a prescribed frequency in theexcited BAW can be extracted.

In this modified example as well, the similar effect as the aboveembodiment can be obtained. Further, in this modified example, namely,in BAW filter, since it is not necessary to form the top electrode film4 into IDT, a minute processing of the top electrode film 4 is notrequired. Further, since BAW filter does not have IDT, it is easy toproduce a filter with lower loss and higher electric power resistancethan SAW filter.

Other Embodiment

As described above, explanation has been given specifically for theembodiments of the present disclosure. However, the present disclosureis not limited thereto, and can be variously modified in a range notdeparting from the gist of the disclosure.

For example, the piezoelectric film device according to the aboveembodiment can function as an actuator by connecting the voltageapplication means between the bottom electrode film (base film) and thetop electrode film. By applying a voltage between the bottom electrodefilm and the top electrode film using the voltage application means, theKNN-film (piezoelectric film) can be deformed. Various members connectedto the piezoelectric film device can be actuated due to the abovedeformation motion. In this case, the piezoelectric film device can beapplied to a head for an inkjet printer, a MEMS mirror for a scanner,and a vibrator for an ultrasonic generator, etc., for example.

Further, for example, the piezoelectric film device according to theabove embodiment can function as a sensor by connecting the voltagedetection means between the bottom electrode film (base film) and thetop electrode film. When the KNN-film is deformed according to avariation of some physical quantity, a voltage is generated between thebottom electrode film and the top electrode film due to the deformation.By detecting this voltage using the voltage detection means, thephysical quantity applied to the KNN-film can be measured. In this case,the piezoelectric film device can be applied to an angular velocitysensor, an ultrasonic sensor, a pressure sensor, and an accelerationsensor, etc., for example.

Further, in the above embodiment, the substrate may be removed from thelaminated substrate when forming the laminated substrate into thepiezoelectric film element, as long as the piezoelectric film deviceproduced using the laminated substrate (piezoelectric film element) isapplied to desired applications such as a high frequency filter.

Preferable Aspects of the Present Disclosure

Preferable aspects of the present disclosure will be supplementarilydescribed hereafter.

Supplementary Description 1

According to an aspect of the present disclosure, there is provided alaminated substrate having a piezoelectric film, including:

-   a substrate; and-   a piezoelectric film provided on the substrate interposing a base    film,-   wherein the piezoelectric film has an alkali niobium oxide based    perovskite structure represented by a composition formula of    (K_(1-x)Na_(x))NbO₃ (0<x<1) and preferentially oriented in (001)    plane direction, and-   a sound speed of the piezoelectric film is 5100 m/s or more.

Supplementary Description 2

Preferably, there is provided the substrate of the supplementarydescription 1, wherein an absolute value |d₃₁| of a piezoelectricconstant of the piezoelectric film is 90 pm/V or more.

Supplementary Description 3

According to another aspect of the present disclosure, there is provideda laminated substrate having a piezoelectric film, including:

-   a substrate; and-   a piezoelectric film on the substrate interposing a base film,-   wherein a sound speed of the piezoelectric film is 5100 m/s or more,    and an absolute value |d₃₁| of a piezoelectric constant of the    piezoelectric film is 90 pm/V or more.

Supplementary Description 4

Preferably, there is provided the substrate of the supplementarydescription 3, wherein the piezoelectric film has an alkali niobiumoxide based perovskite structure represented by a composition formula of(K_(1-x)Na_(x))NbO₃ (0<x<1) and preferentially oriented in (001) planedirection.

Supplementary Description 5

Preferably, there is provided the substrate of any one of thesupplementary descriptions 1 to 4, wherein the sound speed of thepiezoelectric film is 5700 m/s or more.

Supplementary Description 6

Preferably, there is provided the substrate of any one of thesupplementary descriptions 1 to 5, wherein the piezoelectric filmcomprises crystals (alkali niobium oxide) constituting the piezoelectricfilm, and 85% or more of the crystals are oriented in (001) planedirection.

Supplementary Description 7

Preferably, there is provided the substrate of any one of thesupplementary descriptions 1 to 6, wherein a thickness of thepiezoelectric film is 0.5 µm or more and 5 µm or less.

Supplementary Description 8

According to further another aspect of the present disclosure, there isprovided an element having a piezoelectric film or a device having apiezoelectric film, including:

-   a substrate;-   a piezoelectric film provided on the substrate interposing a base    film; and-   an electrode film (pattern electrode film) provided on the    piezoelectric film,-   wherein the piezoelectric film has an alkali niobium oxide based    perovskite structure represented by a composition formula of    (K_(1-x)Na_(x))NbO₃ (0<x<1) and preferentially oriented in (001)    plane direction, and-   a sound speed of the piezoelectric film is 5100 m/s or more.

Supplementary Description 9

According to further another aspect of the present disclosure, there isprovided an element having a piezoelectric film or a device having apiezoelectric film, including:

-   a substrate;-   a piezoelectric film provided on the substrate interposing a base    film; and-   an electrode film (pattern electrode film) provided on the    piezoelectric film,-   wherein a sound speed of the piezoelectric film is 5100 m/s or more,    and an absolute value |d₃₁| of a piezoelectric constant of the    piezoelectric film is 90 pm/V or more.

Supplementary Description 10

According to further another aspect of the present disclosure, there isprovided an element having a piezoelectric film or a device having apiezoelectric film, including:

-   a substrate;-   a bottom electrode film provided on the substrate;-   a piezoelectric film provided on the bottom electrode film; and-   a top electrode film provided on the piezoelectric film,-   wherein the piezoelectric film has an alkali niobium oxide based    perovskite structure represented by a composition formula of    (K_(1-x)Na_(x))NbO₃ (0<x<1) and preferentially oriented in (001)    plane direction, and-   a sound speed of the piezoelectric film is 5100 m/s or more.

Supplementary Description 11

According to further another aspect of the present disclosure, there isprovided an element having a piezoelectric film or a device having apiezoelectric film, including:

-   a substrate;-   a bottom electrode film provided on the substrate;-   a piezoelectric film provided on the bottom electrode film; and-   a top electrode film provided on the piezoelectric film,-   wherein a sound speed of the piezoelectric film is 5100 m/s or more,    and an absolute value |d₃₁| of a piezoelectric constant of the    piezoelectric film is 90 pm/V or more.

Supplementary Description 12

According to further another aspect of the present disclosure, there isprovided a method for manufacturing a laminated substrate having apiezoelectric film, including:

forming a piezoelectric film on a substrate interposing a base film, thepiezoelectric film having an alkali niobium oxide based perovskitestructure represented by a composition formula of (K_(1-x)Na_(x))NbO₃(0<x<1) and preferentially oriented in (001) plane direction, and havinga sound speed of 5100 m/s or more.

Supplementary Description 13

According to further another aspect of the present disclosure, there isprovided a method for manufacturing a laminated substrate having apiezoelectric film, including:

forming a piezoelectric film on a substrate interposing a base film,with its sound speed being 5100 m/s or more and its absolute value |d₃₁|of a piezoelectric constant being 90 pm/V or more.

Description of Signs and Numerals

-   1 Substrate-   3 Piezoelectric film-   10 Laminated substrate

1. A laminated substrate having a piezoelectric film, comprising: asubstrate; and a piezoelectric film on the substrate interposing a basefilm, wherein a sound speed of the piezoelectric film is 5100 m/s ormore, and an absolute value |d₃₁| of a piezoelectric constant of thepiezoelectric film is 90 pm/V or more.
 2. The laminated substrate havinga piezoelectric film according to claim 1, wherein the piezoelectricfilm has an alkali niobium oxide based perovskite structure representedby a composition formula of (K₁-_(x)Na_(x))NbO₃, wherein 0<x<1, andpreferentially oriented in (001) plane direction.
 3. The laminatedsubstrate having a piezoelectric film according to claim 1, wherein thepiezoelectric film contains an element of Cu, Mn, Li, Ta, or Sb in arange of 5 at% or less.
 4. A piezoelectric film element comprising thesubstrate having a piezoelectric film according to claim 1 and anelectrode film provided on the piezoelectric film.
 5. The piezoelectricfilm element according to claim 4, wherein the piezoelectric film has analkali niobium oxide based perovskite structure represented by acomposition formula of (K₁-_(x)Na_(x))NbO₃, where 0<x<1, andpreferentially oriented in (001) plane direction.
 6. The piezoelectricfilm element according to claim 4, wherein the piezoelectric filmcontains an element of Cu, Mn, Li, Ta, or Sb in a range of 5 at% orless.
 7. A method for manufacturing the laminated substrate having apiezoelectric film according to claim 1, the method comprising: forminga piezoelectric film on a substrate interposing a base film, wherein asound speed of the piezoelectric film is 5100 m/s or more, and anabsolute value |d₃₁| of a piezoelectric constant of the piezoelectricfilm is 90 pm/V or more.
 8. The method according to claim 7, wherein thepiezoelectric film has an alkali niobium oxide based perovskitestructure represented by a composition formula of (K_(1-x)Na_(x))NbO₃,where 0<x<1, and preferentially oriented in (001) plane direction. 9.The method according to claim 7, wherein the piezoelectric film containsan element of Cu, Mn, Li, Ta, or Sb in a range of 5 at% or less.